This invention relates to an improvement in a wet disc brake assembly having a set of stationary discs and a set of movable discs wherein a brake coupler is used to selectively couple the movable set of discs to a rotating member only during braking maneuvers.
Wet disc brakes are utilized in many vehicle braking applications. They can also be used in many non-vehicle braking applications. In particular, a number of rotating discs are provided with a friction surface, and are connected for rotation with a wheel hub or other rotating member. The discs are slidable axially along the wheel hub. The rotating discs are interspaced with stationary discs which are connected to an outer stationary member. The stationary discs are also axially slidable relative to the outer stationary member.
A hydraulic chamber is associated with a piston, and when hydraulic fluid is delivered to the chamber, the piston moves to axially compress the rotating and stationary discs together to reduce the rotation of the rotating member relative to the stationary member.
These types of brakes typically include a plurality of interspaced stationary and rotating discs. Often, as many as ten rotating discs are used in combination with eleven stationary discs.
The rotating and stationary discs are mounted within a fluid chamber formed between the stationary and rotating members. During a braking maneuver, the piston forces the stationary and rotating discs together, which increases the friction between the discs. As the friction increases, the rotational speed of the rotating member is decreased.
One disadvantage with this configuration is that during non-braking vehicle operation, the rotating discs are continuously rotating in the fluid stored in the fluid chamber. This creates an undesirable drag effect. Drag decreases the operating efficiency of the rotating member. Additional energy is required to rotate the rotating member at a specified speed due to the drag. The drag also causes premature wear on the rotating disc members.
If drag could be eliminated during non-braking vehicle operations, the wear life of the discs and the operating efficiency of the vehicle could be increased.
In a disclosed embodiment of this invention, a disc brake assembly includes a stationary member and a rotating member supported for rotation with respect to the stationary member. The rotating member defines a central axis of rotation. A first set of discs extends axially along the axis of rotation within the stationary member and a second set of discs is interspaced with the first set of discs. A coupler selectively couples the second set of discs to the rotating member for rotation therewith about the axis.
The coupler couples the second set of discs to the rotating member only when a braking maneuver is initiated. Thus, during non-braking vehicle operation there is no relative rotation between the first and second set of discs and the drag effect is eliminated.
In a preferred embodiment, a first actuator is supported by the stationary member and applies an actuating force to move the coupler into engagement with the rotating member when the braking maneuver is initiated. Once the second set of discs is coupled to the rotating member, a second actuator moves the first set of discs and the second set of discs together to reduce rotation of the rotating member and brake the vehicle. Once the braking maneuver is completed, a first resilient return mechanism moves the first and second set of discs away from one another to allow the rotating member to rotate freely about the axis rotation. A second resilient return mechanism is then used to disengage the coupler from the rotating member such that the first and second sets of discs are stationary relative to each other, i.e., there is no drag.
The preferred inventive method for braking a vehicle wheel with a disc brake assembly includes the steps of: providing the disc brake assembly with a stationary member, a rotating member supported for rotation with respect to the stationary member and defining a central axis of rotation, a first set of stationary discs spaced axially along the axis of rotation within the stationary member, and a second set of discs interspaced with the first set of discs; initiating a braking maneuver; coupling the second set of discs with the rotating member such that the second set of discs rotate with respect to the first set of stationary discs; and moving the first set of stationary discs and the second set of discs together to reduce rotation of the rotating member.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.